CF Card wear optimalisation for ext4

Bodo Thiesen bothie at
Thu Oct 16 16:25:55 UTC 2014

* Andreas Dilger <adilger at> hat geschrieben:

> You can see in the ext4 superblock the amount of data that has been
> written to a filesystem over its lifetime:
> Note that this number isn't wholly accurate, but rather a guideline.

Is is more like a completely bogus value at best:

# LANG=C df -h / | grep root
/dev/root       3.7T  3.6T   73G  99% /
# grep [0-9] /proc/partitions
   8        0 3907018584 sda
# tune2fs -l /dev/sda | grep Lifetime
Lifetime writes:          2503 GB

3.7 TB Disk/Partition, 3.6 TB space in use but only 2.4 TB writes.

No, there are no 1.2 TB + x allocated but never written to clusters on
that file system.

And if /sys/fs/ext4/*/*_write_kbytes are as correct as the "Lifetime
writes" value, than the correct answer to Jelle's question is: "There is
no way currently to figure out the actual number of writes to a device".

Regards, Bodo

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